Aspect ratio is one of those fundamentals that designers know intuitively but rarely formalize as explicit knowledge — until a campaign goes live with the wrong proportions in a placement and someone has to explain why the brand's product photo has an unexpected crop on LinkedIn's company page header.
This is a working reference, not a listicle. It covers the formats you'll encounter most in a typical campaign cycle, what makes each format's constraints distinct, and where the non-obvious decisions live.
The Landscape Formats
16:9 — The Campaign Workhorse
The 16:9 ratio is the base assumption for most display advertising and social feed formats. At 1200×628 pixels, it's the OG image spec. At 1920×1080, it's YouTube's standard video thumbnail and most presentation-format display ads. At 1280×720, it covers the minimum recommended resolution for YouTube thumbnails and most connected-TV ad formats.
The non-obvious thing about 16:9 across platforms: the horizontal center of the frame is not always the visual center. LinkedIn's feed card crops 16:9 assets to approximately 1.91:1 for desktop link previews — that's close to, but not the same as, 16:9, which means an asset designed to precisely 16:9 proportions will have a narrow vertical strip cropped from each side in that placement. If your composition is centered, the cropping is symmetric and probably fine. If your logo or key product element is positioned off-center, verify that it survives the 1.91:1 crop specifically.
3:1 — The Header Strip
3:1 is primarily the Twitter/X profile header ratio, at 1500×500 pixels. LinkedIn's company page banner sits at 1128×191, which is closer to 5.9:1 — it's commonly called a "3:1 header" but the actual ratio is significantly wider. The LinkedIn banner is punishing for brand assets designed to 3:1 proportions; a logo centered in a 3:1 design will be off-center relative to the LinkedIn banner's wider field.
The practical approach for header-strip formats: design to the specific pixel dimensions of the target platform, not to a generic ratio. The "3:1 header" category is too broad to be a safe design target.
1.91:1 — The OG Image Ratio
The Open Graph specification recommends 1200×628 pixels as the standard OG image size, which works out to approximately 1.91:1. This matters because it doesn't nest cleanly inside other ratios — a 16:9 asset scaled down is 1.78:1, which is close but will show edge crops when rendered as an OG image preview by most social platforms. If you're deriving OG images from 16:9 master assets, you need to explicitly account for the 6% width difference.
The Vertical Formats
9:16 — Stories and Reels
At 1080×1920, 9:16 is the full-bleed vertical format for Instagram Stories, Facebook Stories, TikTok, and Snapchat. It's also the most unforgiving format for brand assets originally designed in landscape orientation, because the safe zone constraints are severe: the top 14% and bottom 20% of the frame are occupied by platform UI in most contexts, leaving 66% of the frame as the reliable content area.
That effective content area — roughly 1080×1267 pixels within the 1920-pixel height — is still tall, but for a brand that has horizontal-oriented logos and photography, designing natively for this format requires rethinking the composition rather than just rotating or scaling the landscape asset. A wide-format wordmark logo that reads well at 400px wide in a landscape banner may need to be placed at a different scale, a different position, or in a stacked variant to work in the 9:16 safe area.
4:5 — Instagram Feed Portrait
Instagram's portrait feed format at 1080×1350 (4:5) has become important because it occupies more vertical screen real estate in the feed than a square or landscape post, which affects how much of the feed the post captures before a user scrolls past. It's not a standard format in all platforms' ad unit menus, but for Instagram specifically it deserves explicit treatment in a campaign's format matrix.
The 4:5 ratio sits between square (1:1) and portrait (9:16) and inherits some challenges from both: taller than square means more careful vertical composition, but not so tall that the 9:16 safe-zone constraints around platform UI apply. It's a relatively forgiving format for brand assets with portrait-oriented photography.
The Square Formats
1:1 — The Universal Fallback
At 1080×1080 (or 800×800 for lower-resolution placements), 1:1 is the format that survives best across the widest range of platform contexts. It's the default feed format on Instagram and Facebook, it renders acceptably in most display ad networks, and it's the standard for most e-commerce product thumbnails.
We're not saying 1:1 is always the right format — it isn't. Square compositions can feel static compared to landscape or portrait formats in scroll-heavy contexts. But as the single format that works adequately everywhere when nothing else is specified, it earns its place as a baseline.
The structural challenge with 1:1 for brand assets: logo placement in corners has high variance in readability across placement sizes. A logo in the lower-left of an 1080×1080 frame may be 120px wide and clearly legible at full resolution, but the same file rendered as a 60×60 feed thumbnail makes that logo roughly 6–7px wide — not readable. Designing the 1:1 format with the full range of rendering sizes in mind typically means either centering the logo or using a version of the brand mark designed for small-scale legibility.
Display and Paid Formats
728×90 — The Leaderboard
The leaderboard banner is the oldest standardized display ad unit and remains common on desktop publishing networks and news sites. At 728×90, the aspect ratio is approximately 8:1 — extremely wide relative to height. This makes it nearly unusable for photography-based brand assets and works best with typography-forward designs: logo + tagline, or logo + offer callout.
The temptation with leaderboard banners is to pull elements from a landscape master asset. The result is typically a cramped, hard-to-read version of a design that was never intended for this format. A leaderboard benefits from being designed natively, with elements selected specifically for the format's extreme horizontality.
300×250 — The Medium Rectangle
The IAB medium rectangle (MREC) at 300×250 is a 6:5 ratio — almost but not quite square. It's the highest-volume display ad format in programmatic inventory and should be in every brand team's standard format set for display campaigns. Its near-square proportions mean compositions designed for 1:1 square can often be adapted to MREC with modest adjustments.
Designing Across Ratios Without Starting Over
The practical question for brand designers isn't how to design each format perfectly from scratch — it's how to establish a source composition flexible enough to yield valid designs across the format matrix without starting over for each one.
The approach that works: design your source asset at a resolution and ratio where the critical elements (logo, product shot, headline) are each independently positioned and composited, not merged or flattened. When the format changes, what changes is the canvas size and the layout zone each element occupies — not the elements themselves. A logo with its own layer, clear of the background, can be repositioned to a different anchor point in each format. A logo that's been merged into a background treatment needs to be re-isolated first, which adds time.
Format-aware composition is the design habit that scales across ratio changes. The time invested in keeping source assets compositionally clean pays back across every campaign cycle where format variants are needed.
